Protecting Ocean Ecosystems

Closed Areas Cautionary Tales Pt. 3: Something Rotten in Denmark

A map of the study area. Google Maps.

New England’s fishery managers are poised to allow large scale commercial fishing in thousands of square miles of New England waters, which have long been set aside to protect cod and other struggling fish populations. These groundfish closed areas were put in place following widespread crashes of fish populations in the early 1990’s and were intended to protect juvenile fish, spawning areas and seafloor habitat.  Biological productivity has begun to start showing improvements only recently.

As fishery managers consider re-introducing damaging forms of fishing like bottom trawling into these protected areas, they should also consider the experiences of other fisheries that exploited protected areas. Previously on Talking Fish we looked at the actions that led to commercial extinction of the cod fishery in some Canadian waters, and the collapse of fish populations in Scottish waters after protected areas were removed. The waters between Denmark and Sweden hold another sobering lesson for New England officials.

The Öresund is a narrow strait between Copenhagen and Malmö, Sweden, that serves as the main shipping route to the Baltic Sea. The high volume of ship traffic made use of mobile fishing gears like trawls impractical and they have been banned there since the 1930s. Fishing in the Öresund is mostly done by gill nets. Just to the north is a much larger body of water called the Kattegat, which has been heavily fished for decades by bottom trawls.

A more detailed map of the Kattegat and Oresund between Denmark and Sweden. Map credit: Swedish Institute for the Marine Environment

The Öresund became a de facto protected area. The Kattegat became a poster child of heavy exploitation. And scientists saw an opportunity to draw some comparisons.

In a 2010 report prepared for the European Parliament Henrik Svedang of the Swedish Institute for the Marine Environment explored what had become of the resident populations of bottom dwelling species like cod. Svedang reviewed the relevant studies and found:

“The Kattegat cod stock has steadily declined over the last two decades,” and is “on the verge of extinction.” The cod stock in the Öresund, on the other hand, “is stable and even shows signs of increase in recent years.”

The decline in production from the Kattegat was so severe that over time the much smaller Öresund produced far more fish. Svedang noted that “the cod productivity per area unit is roughly 100 times higher in the Öresund than in the Kattegat.”

In his book, The Ocean of Life: The Fate of Man and the Sea (Viking 2012), marine scientist Callum Roberts drew out the larger lesson from this tale of two waterways. “Fisheries benefit from complexity” in populations, he wrote, “and populations like those in the Öresund are locally adapted.” The bottom trawling fishing of the Kattegard laid waste to that diversity and “in the process it has undermined the capacity of populations, and the fisheries that depend on them, to continue to thrive as conditions change. This adaptability becomes ever more valuable as the world around us changes.”

That last bit is an especially important consideration for New England fishery managers. As climate change threatens fish populations damaged by decades of past overfishing, we must not add to the pressure. Let’s face it—we’re not going to stop climate change in its tracks even if we stopped CO2 emissions tomorrow. So what levers of control do we really have to give cod and other fish a fighting chance? We can control fishing mortality and we can protect habitat. Unfortunately, the New England Council (with NOAA encouragement) seems to be going in the opposite direction. If these fish are facing unprecedented change in the ocean environment it seems profoundly unwise to undo protections as they struggle to adapt.


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